Data communication networks are being developed which enable the flow of information to ever greater numbers of users at ever higher transmission rates. A problem is created, however, when data is transmitted at high rates over a plurality of circuits of the type that comprise multi-pair data communication cable. In particul transmits and receives electromagnetic radiation so that the signals flowing through one circuit or wire pair (the "source circuit") may couple with the signals flowing through another wire pair (the "victim circuit"). The unintended electromagnetic coupling of signals between different pairs of conductors of different electrical circuits is called crosstalk and is a source of interference that often adversely affects the processing and integrity of these signals. The problem of crosstalk in information networks increases as the frequency of the transmitted signals increases.
In the case of local area network (LAN) systems employing electrically distinct twisted wire pairs, crosstalk occurs when signal energy inadvertently "crosses" from one signal pair to another. The point at which the signal crosses or couples from one set of wires to another may be 1) within the connector or internal circuitry of the transmitting station, referred to as "near-end" crosstalk, 2) within the connector or internal circuitry of the r receiving station, referred to as "ear-end crosstalk", or 3) within the interconnecting cable.
Near-end crosstalk ("NEXT") is especially troublesome in the case of telecommunication connectors of the type specified in sub-part F of FCC part 68.500, commonly referred to as modular connectors. Such modular connectors include modular plugs and modular jacks. The EIA/TIA of ANSI has promulgated electrical specifications for near-end crosstalk isolation in network connectors to ensure that the connectors themselves do not compromise the overall performance of the unshielded twisted pair interconnect hardware typically used in LAN systems. The EIA/TIA Category 5 ("Cat-5") electrical specifications specify the minimum near-end crosstalk isolation for connectors used in 100 ohm unshielded twisted pair Ethernet type interconnects at speeds of up to 100 MHz.
While it is desirable to use modular connectors for data transmission for reasons of economy, convenience and standardization, the standard construction of modular jacks inherently results in substantial near-end crosstalk at high frequency operation. In particular, conventional modular jacks generally comprise a plurality of identically configured contact/terminal members that extend parallel and closely spaced to each other thereby creating the possibility of excessive near-end crosstalk at high frequencies.
To reduce the possibility of near-end crosstalk, a high frequency electrical connector assembly is disclosed in U.S. Pat. Nos. 5,639,266 and 5,791,942 (Patel), incorporated by reference herein, and includes two different constructions of contact/terminal members. Specifically, a portion of the contact/terminal members include a "forward facing" contact portion while a remaining portion have a "rearward facing" contact portion. The forward facing contact portions each include a rearward end nearer to the closed end of the connector which is electrically coupled to a respective terminal whereby a forward end of each forward facing contact portion constitutes a free forward end which faces toward the entrance opening of the connector. By contrast, the rearward facing contact portions each include a forward end nearer the entrance opening of the connector assembly which is electrically coupled to a respective terminal whereby a rearward end of each rearward facing contact portion constitutes a free rearward end which faces away from the entrance opening. The forward and rearward facing contact portions are substantially parallel and laterally adjacent to one another.
In one manner of assembly of the connector assembly, the contact/terminal members with a forward facing contact portion are inserted into a contact housing part through a notch formed in the front wall of the contact housing part adjacent the upper surface thereof so that the terminal of each of these contact/terminal member is positioned within a bore in a back portion of the contact housing part and the forward end of the contact portion of each contact/terminal member overlies an upwardly facing stop surface at a front portion of the contact housing part. On the other hand, the contact/terminal members with a rearward facing contact portion are inserted into the contact housing part so that a conductor portion of each contact/terminal member lies flush with an upper surface of the contact housing part. As such, when the contact housing part is inserted into the outer housing part, the contact/terminal members with a rearward facing contact portion are securely pressed between the contact housing part and the outer housing part. However, in view of the depth to which the contact/terminal members with a forward facing contact portion are recessed within the contact housing part, these contact/terminal members cannot be firmly held in place by means of the contact housing part and outer housing part alone. The absence of a firm hold of these contact/terminal members may cause failure when handling the connector assembly during installation on a printed circuit board and during routine mechanical cycling function of the connector assembly.
In view of the foregoing, several techniques have been contemplated in order to firmly secure the contact/terminal members with a forward facing contact portion in the connector assembly.
One method is to apply an amount of epoxy to one or more portions of each contact/terminal member with a forward facing contact portion which engage the connector housing. However, the use of existing epoxies to retain components in an electrical connector assembly is not widely accepted because the epoxy can flow before curing into an area which it will restrict the intended movement of the contact/terminal members, cover insulation material or conductive surfaces, or otherwise prove to be unreliable over the life of the connector assembly.
Another method is to heat stake the contact/terminal members with a forward facing contact portion. This method entails the intentional reflowing of plastic material, i.e., heating a plastic portion formed on the connector housing for this purpose, over one or more portions of the contact/terminal members so that upon re-solidification of the plastic material, the contact/terminal members are firmly embedded in connection with the connector housing. However, heat staking often fails to provide a reliable bond and may therefore cause failure during routine handling of the connector assembly when installing the same on a printed circuit board and during routine mechanical cycling function of the connector assembly.